内科学肺结核(八年制).ppt

* Infection with tuberculosis is almost exclusibely spread from person to person by airborne transmission. Tiny particles containing tubercle bacili , 1-5uM in size and enveloped in an aerosol droplet, are expelled into the air primarily when someone with pulmonary or laryngeal tuberculosis coughs or sneezes. These microscropic infectious particles can remain suspended in air for extended periods of time . If a new host inhales the air contaminated by these dropledt nuclei, transmission may occur. Larger particles fall out of suspension and are deposited on the mucociliary escalator lining the airways and are simply expectroated or swallowed . Smaller droplet nuclei are not depositedd on the airway mucosa but are transported by air currents primarily to the periphery of the lower lung aoned and deposited ont the surfaces of alveoli, where they may be ingested by alveolar macrophages and destroyed.or as happens in certain instances, the tubercle bacillus may multiply. Following inhalation, any one of several outcomes is possible. 1)the tubercle bacillus can be eliminated immediately( no infection). 2) or can remain dormant in the host indefinitely (infection without disease, as occurs in the majority (90%) of persons, who are free of disease but remain infected with M.tubercuiosis for the rest of their lives. 3) the organis can immediately or rapidly cause tuberculosis (primary tuberculosis), as occurs in approximately 5% of perons, ih ehom tuberculosis develops ih the first or second year following infection. 4) the tuvercle bacillus can cause disease many years after infection has occurred (recrudescent tuberculosis). As occurs in about 5% of patients. So, disease develops at some point during their lifetime in only about 10% of persons infected with M,tuberculosis. 易感人群：除遗传因素之外，还包括生活贫困、居住拥挤、营养不良等社会因素。婴幼儿、老年人、HIV、免疫抑制剂使用者、慢性疾病患者等 * 影响传染性的因素： 化学治疗对传染性的影响：治疗后呈对数减少，涂阳负荷为10+7/mL，2周后为5%，4周后为0.25%。 * 发病有两种方式：1.潜伏的结核分枝杆菌 ，内源性复发 2.外源性重染。 继发和原发有显著区别，后者